How to re-start the Matlab-interface

STRUREL offers an interface to Matlab: You can evaluate Matlab functions or Matlab scripts within a limit-state function call.

The initial start of the Matlab engine takes a bit. Therefore, to be able to evaluate your Matlab-based limit-state function calls efficiently, we keep the Matlab engine running in the background. You need to be aware of this behavior, if you work with external Matlab scripts: When you change the content of your script, you need to manually restart the Matlab engine. Otherwise, the Matlab engine will not take the changes you made into account.

The simplest way to force a re-load of the engine is to close the Matlab engine actively. Add the following code in the ‘Symbolic Expressions‘ tab of STRUREL:

FLIM(2)=matlabf("%quit")

Now, you simply have to evaluate this limit-state function each time you want to enforce a re-start of the Matlab engine.

Use a Matlab script as limit-state function

In one of the previous posts, we showed you how to work with in-line Matlab functions directly in STRUREL. Did you know? You can also use a Matlab script as limit-state function in STRUREL.

Again, we use the example limit-state function RS that we already used in the past: Our stochastic model consists of the two random variables R and S, where R represents the resistance of a system of interest and S is the system load. The symbolic expression for the corresponding limit-state function in the native syntax of STRUREL would be:

FLIM(1) = R-S

However, if you have Matlab installed on your system and if the Matlab interface of STRUREL is configured correctly, you could also use the following expression:

FLIM(1) = matlabs("my_model")

where my_model.m is a Matlab script file located in the same directory as the iti-file of STRUREL.

For the example at hand, the Matlab script file should look as follows:

function [lsfval] = my_model(INPUT)

R = INPUT(1);
S = INPUT(2);

lsfval = R - S

end

The ordering of the random variables in the vector INPUT corresponds to the order in which they appear in the stochastic model of STRUREL.

Alternatively, the Matlab script file could look as follows:

function [lsfval] = my_model(INPUT)

global R;
global S;

lsfval = R - S

end

where the variable names R and S must match the names of the random variables of the stochastic model of STRUREL.

By means of the STRUREL command matlabs, you can integrate any limit-state function written in Matlab-Syntax directly in your reliability analysis performed with STRUREL.

How to use in-line Matlab in Strurel

In the last post, we showed you how to work with in-line Python functions directly in STRUREL. Did you know? You can also use in-line Matlab functions directly in a symbolic expression in STRUREL.

For example, assume a problem for which you have the two random variables R and S in your stochastic model, where R represents the resistance of a system of interest and S is the system load. The symbolic expression for the corresponding limit-state function in the native syntax of STRUREL would be:

FLIM(1) = R-S

However, if you have Matlab installed on your system and if the Matlab interface of STRUREL is configured correctly, you could also use the following expression:

FLIM(1) = matlabf("R-S")

Sure, calling the Matlab interpreter for this simple demonstration example is like taking a sledgehammer to crack a nut. However, the interface-function matlabf is a tool that gives you access to the full power of Matlab directly in the symbolic expression of STRUREL.